Stability control systems for automotive vehicles have recently begun to be offered on various products. Stability control systems typically monitor the dynamic behavior of the vehicle to prevent or control unstable driving characteristics. For example, yaw control systems typically control the yaw of the vehicle by regulating the braking effort at the various wheels of the vehicle. Similarly, roll control systems typically control the roll or tilt of the vehicle by regulating the braking effort at the various wheels, typically the outside wheels in a turn.
Typically, the stability control system utilizes a sensor cluster including at least a lateral acceleration sensor, a longitudinal acceleration sensor, a speed sensor, and a steering angle sensor. The sensor cluster may also include a yaw rate sensor, a roll rate sensor, and a pitch rate sensor. Based on information from the sensor cluster, the stability control system will determine the potential for unstable conditions and apply a corrective action, typically through braking of the wheels or by modifying the tire steering direction. A model is created for each particular vehicle so that the stability control system can recognize when the information obtained from the sensors indicates a propensity for vehicle instability. That is, since the dynamics of a vehicle are individual to that vehicle, different critical values are used to determine vehicle instability.
Unfortunately, the vehicle reference model, such as a yaw rate reference model, does not always accurately represent the vehicle for every loading condition. That is, when the vehicle is in a loaded condition, the yaw rate reference model may be inaccurate. Thus, during certain driving maneuvers, the control strategy that is beneficial for an unloaded vehicle is not necessarily appropriate for a loaded vehicle. Accordingly, there exists a need to provide a stability control system that accurately represents the vehicle for all loading conditions.